Chemical elements
  Tungsten
    Isotopes
    Energy
    Production
    Preparation
    Application
    Physical Properties
    Chemical Properties
    Compounds
      Tungsten Hexafluoride
      Tungsten Oxyfluorides
      Tungsten Dichloride
      Double Chlorides of Trivalent Tungsten
      Tungsten Tetrachloride
      Tungsten Pentachloride
      Tungsten Hexachloride
      Tungsten Oxychlorides
      Tungsten Dibromide
      Tungsten Pentabromide
      Tungsten Hexabromide
      Tungsten Chlorobromides
      Tungsten Oxybromides
      Tungsten Di-iodide
      Tungsten Tetra-iodide
      Tungsten Dioxide
      Ditungsten Pentoxide
      Tungsten Trioxide
      Tungstic Acid
      Aluminium Tungstates
      Ammonium Tungstates
      Antimony Tungstates
      Barium Tungstates
      Normal Bismuth Tungstate
      Cadmium Tungstates
      Calcium Tungstates
      Cerium Tungstate
      Chromium Tungstates
      Cobalt Tungstates
      Copper Tungstates
      Indium Tungstate
      Iron Tungstates
      Lanthanum Tungstate
      Lead Tungstates
      Lithium Tungstates
      Magnesium Tungstates
      Manganese Tungstates
      Mercury Tungstates
      Neodymium Tungstate
      Nickel Tungstates
      Platinum Tungstates
      Potassium Tungstates
      Praseodymium Tungstate
      Rubidium Tungstates
      Samarium Tungstate
      Silver Tungstates
      Sodium Tungstates
      Strontium Tungstates
      Thallium Tungstates
      Tin Tungstates
      Uranium Tungstate
      Ytterbium Tungstates
      Yttrium Tungstate
      Zinc Tungstates
      Metatungstic Acid
      Ammonium Metatungstate
      Barium Metatungstate
      Cadmium Metatungstate
      Calcium Metatungstate
      Cerium Metatungstate
      Cobalt Metatungstate
      Lead Metatungstate
      Magnesium Metatungstate
      Mercurous Metatungstate
      Nickel Metatungstate
      Potassium Metatungstate
      Rubidium Metatungstate
      Samarium Metatungstate
      Silver Metatungstate
      Sodium Metatungstate
      Strontium Metatungstate
      Thallous Metatungstate
      Zinc Metatungstate
      Pertungstic Acid
      Tungsten Bronzes
      Potassium Tungsten Bronze
      Lithium Tungsten Bronze
      Lithium Potassium Tungsten Bronze
      Sodium tungsten bronzes
      Tungsten Disulphide
      Tungsten Trisulphide
      Thiotungstates
      Tungsten Diselenide
      Tungsten Triselenide
      Tungsten Phosphides
      Tungsten Diphosphide
      Tritungsten Tetraphosphide
      Tungsten Monophosphide
      Tungsten Subphosphide
      Phosphotungstic Acids
      12-Tungstophosphoric Acid
      11-Tungstophosphates
      21:2-Tungstophosphoric Acid
      10-Tungstophosphoric Acid
      9-Tungstophosphoric Acid
      17:2-Tungstophosphates
      3-Tungstophosphates
      Hypophosphotungstates
      Tungsten Diarsenide
      Tungsten Chloro-arsenide
      12-Tungsto-arsenates
      11-Tungsto-arsenates
      9-Tungsto-arsenic Acid
      17:2-Tungsto-arsenates
      Tungsto-arsenites
      Tritungsten Carbide
      Ditungsten Carbide
      Tungsten Monocarbide
      Tungsten Iron Carbides
      Tungstocyanic Acid
      Ammonium Tungstocyanide
      Calcium Tungstocyanide
      Cadmium Tungstocyanide
      Caesium Tungstocyanide
      Lead Tungstocyanide
      Magnesium Tungstocyanide
      Manganese Tungstocyanide
      Potassium Tungstocyanide
      Rubidium Tungstocyanide
      Silver Tungstocyanide
      Sodium Tungstocyanide
      Strontium Tungstocyanide
      Thallium Tungstocyanide
      Zinc Tungstocyanide
      Tungsticyanic Acid
      Tungsten Sesquisilicide
      Tungsten Disilicide
      Tungsten Trisilicide
      12-Tungstosilicic Acid
      Iso-12-tungstosilicic Acid
      10-Tungstosilicates
      Tungsten Boride
      12-Tungstoboric Acid
      Iso-12-tungstoboric Acid
    Alloys
    PDB 1aor-2rav
    PDB 2rb5-6fit

Pertungstic Acid, H2WO5






By the action of hydrogen peroxide on solutions of tungstic acid and tungstates, compounds analogous to the persulphuric acids and persulphates are obtained. By dissolving tungsten trioxide in a 2 per cent, hydrogen peroxide solution at the boiling-point, and evaporating the resulting solution, a yellow amorphous mass results, of composition WO3.H2O2.H2O and soluble in water to an acid solution.

Several sodium salts have been prepared:

Na2W2O8.2H2O is obtained as white radiating crystals by the addition of hydrogen peroxide to a hot solution of sodium paratungstate and evaporation of the mixture in a vacuum. The crystals are easily soluble in water.

Na2W2O9.6H2O results as a yellowish-white crystalline powder when the above mixture of paratungstate and hydrogen peroxide is precipitated with alcohol. In this salt the ratio of WO3 to active oxygen, as determined by titration with potassium permanganate in sulphuric acid solution, is 1:1, whilst in the above dihydrate it is 2:1; this suggests that the latter is derived from an acid of constitution 2WO3.H2O2, i.e. H2W2O8, and the former from an acid of constitution WO3.H2O2, i.e. H2WO5, of which H2W2O9 is an anhydro-acid (i.e. 2H2WO5 - H2O ).

By the addition of cooled hydrogen peroxide and aqueous sodium hydroxide solutions to a cooled solution of sodium pertungstate, prepared according to the former method described above, precipitating with alcohol at -12° C. and drying the resulting product in the air, compounds of composition Na2O2.WO4.H2O2 and Na2O2.WO4. H2O2 + (Na2O2)2WO4 + 7H2O have been obtained. These are unstable compounds, although more stable than the corresponding molybdenum compounds; they gradually lose oxygen on standing in air, whilst water causes rapid evolution of oxygen, hydrogen peroxide being found in the resulting solution.

The potassium salt, K2O4.WO4.H2O, is similarly produced by the action of hydrogen peroxide and potash on potassium pertungstate. It is more stable than the sodium salts, but explodes when rubbed or heated to 80° C.


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